Characterisation of the Pressure Dependent Friction Behaviour in an Asymmetric Hydraulic Cylinder: An Empirical Approach

Pedersen, Niels ; Jørgensen, Stefan Melvad

4. term

Energy Engineering, Master

2017

2017-06-01

164 pages

This thesis concerns an investigation of the pressure dependency in the friction force present in an asymmetric hydraulic cylinder. To characterise the pressure dependency, a test setup is designed and constructed where accurate measurements of the friction force and velocity is of great importance. A decentralised control strategy is designed to control the two pressures and velocity of the test cylinder (Ø50/35). With basis in the Modified LuGre model a velocity dependent friction model is proposed. This is partly validated by measurements. Furthermore an investigation of different methods to estimate the friction model parameters is made. A robust sequential method, where the steady state parameters are estimated from steady state measurements and the dynamic parameters are estimated using a Non-Linear Least Sqaures Method (NLSM), is proposed. The pressure dependency of the friction model parameters are investigated for pressures from 20-200 bar. During these tests a position dependent friction was detected due to a lack of break in of the cylinder. A pressure dependency in $F_c$ and $F_s$ was indicated, yet further measurements should be conducted to further characterise the pressure dependency. Furthermore it is indicated that the friction force is behaving dynamically with pressure, though this is not further evaluated.

Friktion ; Hydraulik ; Parameterestimering ; Trykafhængighed ; Systemdesign

Download
View record in AAU Student Projects